1. Field of the Invention
The present invention relates to a contact type image sensor and, more particularly, to a contact type image sensor comprising a light source for emitting the light with a predetermined inclination angle in the direction of a normal line of the surface of an original locating at the position of a read line, an original supporting member for leading the light from the light source to the read line and for supporting the original; and a photoelectric converting device section to receive the light from the original surface.
2. Related Background Art
An example of a construction of a conventional contact type image sensor will now be described hereinbelow.
FIG. 1 is a plan view showing an example of a construction of the conventional contact type image sensor. FIG. 2 is a cross sectional view of FIG. 1. As shown in FIGS. 1 and 2, the contact type image sensor of the constructional example comprises: an LED array 3 in which a plurality of LED devices 2 to irradiate lights to an original 8 are arranged in correspondence to an original read line 9 of the upper surface of a cover glass 6 as an original supporting member so as to have a length corresponding to a width of original 8 to be read; a lens array 1 to lead the reflected lights from the original 8; a sensor array 5 which is constructed by arranging photoelectric converting devices 4 for receiving the lights led by the lens array 1 and for converting into the electric signals; and a frame body 7 to position the above component elements.
However, in case of reading an original having concave and convex surfaces such that a plurality of original papers are adhered onto a base paper, if the LED array 3 as a light source is merely arranged for the read line 9 so as to have a predetermined angle from one side like the contact type image sensor of the above conventional constructional example, shadows are formed on the original 8 by the convex portions and the sensor array 5 reads such shadows, so that the shadows eventually appear as lateral lines on an output image.
To avoid such a phenomenon, a contact type image sensor with a constructional example as shown in FIG. 3 is used as a sensor to read the original having concave and convex portions. According to the contact type image sensor of the present constructional example, by symmetrically arranging the LED arrays 3 and 3' on both sides for the read line 9 with respect to the left and right, the occurrence of the shadows is prevented.
In the contact type image sensor of the constructional example shown in FIG. 3, since two LED arrays are necessary and the costs are high. Therefore, a contact type image sensor with a constructional example as shown in FIG. 4 has been proposed. As shown in FIG. 4, according to the contact type image sensor of the constructional example, the LED array 3' in FIG. 3 is eliminated and a mirror 10 is arranged at the position corresponding to the LED array 3', the reflected light from the original by the LED array 3 is received, and the reflected light is reflected and is again returned to the original, thereby obtaining an effect similar to that in case of the construction of FIG. 3 and reducing the costs.
In the contact type image sensor of the constructional example shown in FIG. 3, however, since it is necessary to keep two spaces enough to enclose the light sources, a long optical path length is needed and the size is large. As compared with the reduction type, a compactness as one of large advantages of the contact type is largely obstructed. The necessity of two light sources becomes a cause of an increase in costs.
According to the contact type image sensor with the constructional example shown in FIG. 4, on the other hand, since the reflected light amount of the mirror 10 depends on the reflected light amount of the original, the reflected light amount of the mirror is largely fluctuated due to a reflection density of the original. Particularly, in case of reading the original of a large density, the reflected light amount is small and an enough effect cannot be obtained.